1. First results from the isopycnic ocean carbon cycle model HAMOCC & MICOM/BCM Karen Assmann, Christoph Heinze, Mats Bentsen, Helge Drange Bjerknes Centre for Climate Research, Bergen, Norway

2. “The choice of vertical coordinate…” “… is the most important aspect of a model’s design” Griffies et al. (2000) AdvantagesDisadvantages z Simple discretization No pressure gradient problems Accurate equation of state Mixed layer representation Tracer advection and diffusion Bottom boundary layer representation  Accurate equation of state Tracer advection and diffusion Pressure gradient problems  Tracer advection and diffusion No pressure gradient problems Thermocline representation Bottom topography representation Mixed layer representation Simplified equation of state Bottom boundary layer representation

3. Ocean ( + sea ice) component of the Bergen Climate Model Global domain with 2.4° horizontal resolution 35 vertical layers including a mixed layer with freely evolving , T, S Climatological NCEP-based forcing & surface restoring 100-year spinup before HAMOCC is started MICOM Miami Isopycnic Coordinate Ocean Model

4. Layer distribution in MICOM Meridional Section Atlantic Ocean

5. Temperature & Salinity in the Atlantic Observations WOA 05 Model Annual Mean Year 180

6. Ocean carbon cycle model of the NPZD (Nutrient-Phytoplankton- Zooplankton-Detritus) class Biogeochemical tracers are transported by MICOM's advection and mixing routines Main changes for use with isopycnic coordinates included amending the implicit sinking scheme and re-defining the euphotic zone Biogeochemical tracer fields are initialised HOMOGENEOUSLY HAMOCC5.1 HAMburg Ocean Carbon Cycle Model

7. Phosphate AtlanticPacific Simulated Annual Mean Year 170 [  mol / l ] Observed WOA05 [  mol / kg ]

8. Phosphate – Spinup Evolution Atlantic Pacific Year 170 Year 50 Year 110

9. Annual Mean Global Primary Production Simulated Annual mean for Year 180 [ g C /m 2 /a] Global Sum: 61 Gt/a Derived from satellite data [ g C /m2 /a] Image from: http://marine.rutgers.edu/opp/ SeaWifs data corrected following Behrenfeld & Falkowski 1997 0 150 300 450

10. Export Production & EF Ratio Export Production Annual Mean Year 180 [ Gt C/m2/a] Global Sum: 8.9 Gt C/a EF Ratio = EP/PP Annual Mean Year 180 Global Mean: 0.14

11. Outlook Model Development: Update to the most recent version of MICOM Inclusion of recent developments in HAMOCC Inclusion of sediment scheme Testing of an aggregate sinking scheme Fine tuning of biological production/euphotic zone during the spin-up run Comparison of HAMOCC in physical models with differing vertical coordinate (MICOM and MPI-OM) Same horizontal grid & atmospheric forcing for both models Investigate effect of model physics on biogeochemistry Development of BESM/BC4M (see also Poster by Kristof Sturm)